GB2027048A

GB2027048A - Soap Powder

Info

Publication number: GB2027048A
Application number: GB7926830A
Authority: GB
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1978-08-03
Filing date: 1979-08-01
Publication date: 1980-02-13
Also published as: GB2027048B

Abstract

A spray-dried or spray-cooled soap powder contains about 20 to 60% of a C8-24 fatty acid salt as the major detergent active component. The powder additionally contains 0.1 to 3% by weight of a particulate, water-soluble acid such as citric acid, tartaric acid, sulphamic acid, ethylene diamine tetraacetic acid, ethanehydroxy, diphosphonic acid, or sodium dihydrogen phosphate as a wetting aid. Inclusion of the acid aids dissolution of the powder and reduces the formation of clots.

Description

SPECIFICATION Manufacture of Soap Powders This invention relates to washing powders based on soap as the principal organic detergent active species.

Washing powders containing relatively large amounts of soap are quite popular in some countries, where they are used largely for washing clothes by hand or in non-automatic washing machines of the single tub or twin-tub type. Although powders based on soap generally have good dissolving properties at the normal wash temperature of 400C and above, great care must be exercised when adding the powder to the water to prevent clots of soap gels being formed. Such clots are unsightly and can take a considerable time to dissolve so that there is a danger of their being left on the washed clothes.

It has been found that the likelihood of soap clots being formed can be very much reduced if the powder is wetted easily by the water.

A number of factors influence the ease with which a powder is wetted, and these include the basic formulation, the conditions under which it is spray-dried and the subsequent processing which it receives.

We have now discovered that a powder based on soap as the principal organic detergent active species is wetted more easily if subsequent to spray-drying, it is mixed with a small quantity of a solid, water soluble acid.

Accordingly, the present invention provides a spray-dried or spray-cooled soap powder comprising from 20 to 60% by weight of a salt of a C824 fatty acid as the sole or principal organic detergent active compound, additionally comprising from 0.1 to 3% by weight of a particulate, watersoluble acid as a wetting aid.

The salt of the C824 fatty acid is preferably present as a sodium or potassium salt, or a mixture thereof.

Preferable the level of the water-soiuble acid is from 0.5 to 2.5% by weight of the spray-dried powder and the acid is selected from one of the following: citric acid, tartaric acid, sulphamic acid, ethylene diamine tetraacetic acid, ethane hydroxydiphosphonic acid or sodium dihydrogen phosphate.

Sodium and potassium salts of C824 fatty acids may, if desired, contain a proportion of unneutralised fatty acid. Thus un-neutralised acid is not included within the 0.1 to 3% of water-soluble acid which may be present in the soap powder of the invention.

The C824 fatty acids from which the sodium potassium soaps are prepared may be derived, for example, from nut oils such as coconut oil or palm kernel oil or from tallow class fats, such as beef and mutton tallows, palm oil, lard, some vegetable butters, castor oil and rape seed oil. The longer carbon chain iength material such as the castor oil, the tallow class fat and the rape seed oil, may be hardened, if desired, so as to decrease the content of unsaturated acids such as oleic acid and linoleic acid.

Without wishing to be limited by theory, we believe that a contributory factor to the efficacy of the invention is the relative particle size of the particulate acid and the soap powder granule. We believe that as water enters the mass of soap powder granules, it first dissolves the relatively finelydivided acid, and the lowering in the pH of the water results in faster dissolution of the alkaline soap granules.

We prefer that the soap granules are between 50 ,t4 and 1000 y average diameter and that the particulate acids are between 25 ,u and 250 ,u.

It is preferred to use mixtures of soaps derived from tallow class fats (C,4~20, mainly C18 fatty acids) and soaps from soft oils and nut oils, which are predominantly C,0~,4, mainly C,2 fatty acids of which normally at least 75% are saturated. In general, the nut oils contribute the lower carbon chain length soaps which improve the solubility of the soap. However, the nut oils are generally more expensive than the tallow class oils and so it is desirable to reduce their inclusion to the minimum that is compatible with good solubility. Typical mixtures consist of from 9 parts tallow class fat to 1 part nut oil soap, to equal parts of each.

The soap powder of the invention may also contain a detergency builder compound. Any detergency builder may be used, either a phosphate-based builder such as sodium tripolyphosphate, sodium pyrophosphate or sodium orthophosphate, or a mixture thereof, or any one of the compounds which has been suggested recently as a result of pressure from those wishing to reduce phosphate contents of effluents. Typical of these are sodium citrate, aluminosilicates, both crystalline and amorphous, and a host of organic chelating compounds, prominent amogst which are nitrolotracetic acid, which has been used commercially in some countries, alkenyl succinate salts and salts of carboxymethyloxysuccinic acid, and salts of dipicolinic acid.These detergency builder compounds can be used in any desired combination so that the desired calcium/magnesium building capacity is achieved at the level of phosphorus, if any, which is permitted or required.

Bearing in mind that soap formulations are to a large extent self-building, the amount of detergency builder compound required will normally be between 5 and 25% by weight of the whole powder formulation when the amount of soap is between 25 and 60% by weight, as is preferred.

The soap powders of the invention may contain other materials in conventional amounts. For example, they may contain a bleaching material, either an oxygen bleach such as sodium perborate or sodium percarbonate, or a chlorine bleach such as sodium di- or tri-chloroisocyanurate, or mixtures thereof. These materials may be present in amounts of from 10 to 30% by weight of the powder, preferably 1 5 to 25%, when the bleaching material is sodium perborate or sodium percarbonate and from 5 to 20% by weight when it is a chlorine bleach such as sodium dichloroisocyanurate.

Anti-redeposition agents, such as sodium carboxymethyl cellulose, fillers such as sodium sulphate, corrosion inhibitors such as sodium silicate, optical brightening agents, coloured speckles and perfumes, may also be present in amounts varying from 0.1 to 5% by weight. Moisture may be present in an amount of up to 15%.

The invention will be further illustrated by reference to the following Example.

Example The following experiment was performed in order to assess the overall solubility of a soap powder used for washing by hand, by estimating (a) the ease with which the powder is wetted, (b) its propensity to clot, and (c) the rate at which it dissolves.

A clear plastics bowl was graduated at a content of 5 litres and filled to the graduation with water of 150 French hardness at a temperature of 450C.

30 gms of the powder to be tested were poured onto the surface of the water during a five second period and after a further five seconds the volume of powder remaining unwetted on the surface was estimated. The water was then agitated and the time noted for any clots formed to breakup and dissolve. The time to complete dissolution of the powder was also noted.

The volume of powder remaining unwetted, the time taken for any clots to disappear and the time taken for complete dissolution were each rated on a scale of O to 5, as shown in Table 1.

Table 1 Wettability Clotting Dissolving % remaining Time for clots Time for powder Grade unwetted Grade to disappear Grade to disappear 5 0 5 5 sec 5 10 sec 4 20 4 10 sec 4 15 sec 3 40 3 15 sec 3 20sec 2 60 2 20 sec 2 30 sec 1 80 1 30 sec 1 40 sec 0 100 0 30 sec 0 40 sec The above experiment was performed on nine soap powders having the following formulations: Component % by weight Sodium soap 43.0 Coconut monoethanolamide 2.5 Sodium tripolyphosphate 8.5 Sodium silicate 8.0 Sodium carbonate 2.0 Sodium perborate (tetrahydrate) 26.0 Tflis was designated Powder No. 1 and eight other powders were formulated by addition of the following components in the stated amounts.

Amount {% by weight of Powder No. Component Powder 1) 2 Sulphamic acid powder 1 3 Sulphamic acid powder 2 4 EDTA* acid powder 1 5 EDTA* acid powder 2 6 Sodium dihydrogen phosphate crystals 2 7 Sodium dihydrogen phosphate powder 1 8 Sodium di hydrogen phosphate powder 2 9 Citric acid powder 1 *EDTA acid is ethylene diamine tetraacetic acid.

The rating given to the nine powders for the three aspects of overall solubility were as shown in Table 2.

Table 2 Ratings Wettability Clotting Dissolving Powder No. grade grade grade 1 0 5 5 2 3 5 5 3 5 5 5 4 4 5 5 5 5 5 5 6 4 5 5 7 4 5 5 8 3 5 5 9 3 5 5 It can be seen from Table 2 that addition of a small quantity of solid, water-soluble acid to a soap powder has a pronounced effect in improving the overall solubility of the soap powder.

Claims

1. A spray-dried or spray-cooled soap powder comprising from 20 to 60% by weight of a salt of a C824 fatty acid as the sole or principal organic detergent active compound, comprising from 0.1 to 3% by weight of a particulate, water-soiuble acid as a wetting aid.

2. A powder according to claim 1, wherein the salt is a sodium or potassium salt.

3. A powder according to claim 1 or claim 2, comprising from 0.5 to 2.5% by weight of the acid.

4. A powder according to any preceding claim, wherein the acid comprises citric acid, tartaric acid, sulphamic acid, ethylene diamine tetraacetic acid, ethane hydroxy diphosphonic acid, sodium dihydrogen phosphate or a mixture thereof.

5. A powder according to any preceding claim, wherein the acid is citric acid.

6. A powder according to any preceding claim, wherein the average diameter of the soap powder granules is from 50 to 1000 microns.

7. A powder according to claim 6, wherein the average diameter of the acid particles is from 25 to 50 microns.

8. A powder according to any preceding claim, comprising from 5 to 25% by weight of a detergency builder.

9. A powder according to claim 8, wherein the detergency builder comprises sodium tripolyphosphate.

10. A spray-dried or spray-cooled soap powder comprising from 0.1 to 3% by weight of a particulate water-soluble acid, substantially as hereinbefore described with reference to powders 2 to 9 of the Example.